1. Field of the Invention
The present invention relates to a downhole tool having a port for fluid communication through a tubular string and operations of the downhole tool. More particularly, the present invention relates to a ported tool having a non-elastomeric seal mechanism and operation thereof. More particularly still, the present invention relates to a ported stage tool suitable for cementation applications.
2. Description of the Related Art
Cementing a well protects possible production zones behind the casing against salt water flow and protects the casing against corrosion from subsurface mineral waters and electrolysis from outside. Cementing also eliminates the danger of fresh drinking water and recreational water supply strata from being contaminated by oil or salt water flow through the borehole from formations containing these substances. It further prevents oil well blowouts and fires caused by high pressure gas zones behind the casing and prevents collapse of the casing from high external pressures which can build up under ground.
A cementing operation for protection against the above described downhole conditions is accomplished by flowing the cement slurry down the casing and back up the outside of the casing in the annulus between the casing and the borehole wall. As wells are drilled deeper and deeper, it has become more difficult to successfully cement the entire well from the bottom of the casing. Multiple stage cementing has been developed to allow the annulus to be cemented in separate stages, beginning at the bottom of the well and working upwardly.
Multiple stage cementing is achieved by placing cementing tools, which are primarily valved ports, in the casing or between joints of casing at one or more locations in the borehole. The cement is flowed through the bottom of the casing and up the annulus to the lowest cementing tool in the well. The bottom is then closed off and the cementing tool is opened to expose the port. Thereafter, cement is flowed through the cement tool up the annulus to the next upper stage. The process is repeated until all of the stages of cementing have been completed.
Generally, the ports of the cementing tools are sealed using an elastomeric seal. However, in some instances where gas flow is encountered, the elastomeric seal may fail, thereby allowing gas to flow and communicate between the annulus and the interior of the casing.
There is a need, therefore, for an improved sealing mechanism for a cementing tool. There is also a need for a ported tool having a non-elastomeric seal mechanism.